Process for making needle felts



Patened Mai- 16,

. 2,437,689 PROCESS FOR MAKING NEEDLE FELTS Carleton 8. Francis, Jr.,

assignor, by mesne assignments. Viscose Corporation, Wilmington,

poration of Delaware West Harwich, Mass., to American Dei., a cor- NoDrawing. Original application October 23,

1939, Serial No. 300.876. piication April 11, 1944, Serial No. 530,553

This invention relates, in general, to felted fibrous structures, and,in particular, to a process for producing felts and includes correlatedimprovements designed to enhance the properties, characteristics and toextend the uses of the felts so produced. This application is a divisionof my copending application Serial No. 300.876, filed October 23, 1939,which in turn is a continuation-inpart of application Serial No.157,018, filed August 2, 1937 (now Patent 2,253,000).

It has previously been impractical to make felts from fibres other thanwool and like fibres which have a substantial curl and, even moreimportant, a rough surface. When attempts are made to produce felts fromsmooth-surfaced and relatively straight fibres such as artificialfibres, the products produced invariably lack strength, and in manycases are devoid of any felt structure whatever, because the smoothsurface of the fibres and their relatively straight form prevents thefibres from interfelting and clinging together in the manner of woolfibres. Even when artificial fibres have been given an artificial crimpor curl, they do not make satisfactory felts because the smooth-surfacedfibres slide upon one another and are not fixed in position by thefelting operation.

It is a general object of the present invention to provide a method forproducing felts from relatively smooth surfaced and/or relativelystraight fibres.

Another object of the invention is to provide an improved felt fromsmooth-surfaced and/or relatively straight fibres, such felts havingcertain desirable characteristics among which are increased strength andgreater tenacity between component fibres and improved wet strength.

A specific object of the invention is to provide a shaped feltedstructure adapted for use as a substitute for woven fabrics and whichmay be manufactured according to the'invention at less cost and withless expenditure of time than woven fabrics.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

In accordance with the present invention, felts of substantial strengthand high tenacity are made from a mixture of normally non-felting fibreand synthetic resin fibres, the non-felting fibres being maintained in afelted condition by the thermal tackiness of the resin fibres. Theprocess of the present invention may be carried out by mixing togethernormally non-felting fibres with synthetic resin fibres which arenontacky at room temperature, but which become Divided and this ap- 5Claims. (01- 154-101) tacky below the temperature at which thenonfelting fibres are damaged, felting the mixture of fibres, heatingthe felted mixture to a temperature at which the resinous fibres becometacky and cooling the felt to effect fibre adhesion. The resin fibresmay be rendered tacky during or after the felting operation and the feltis preferably subjected to pressure while the resin is in an adhesivecondition. The expression "felt" as used in the specification and claimsis intended to include both textile felts and unwoven felted structuresformed therefrom. Paper felts are not claimed herein since such feltsare claimed in my copending U. 8. application Serial No. 444,438, filedMay 25, 1942.

Thus the present invention enables improved felts to be made fromvarious natural or synthetic fibres and filaments which aresmooth-surfaced and/or relatively straight and which do not feltreadily. Among the natural fibres which may be used are cotton, flax,Jute. kapok, silk, and the like, or they may be synthetic fibres ofcellulosic composition, such as a cellulose hydrate, cellulosederivatives, as cellulose esters, mixed cellulose esters, celluloseethers, mixed cellulose esterethers, mixed cellulose ethers, cellulosehydroxyethers, .cellulose carboxy-ethers. cellulose etherxanthates,cellulose xantho-iatty acids. cellulose thiourethanes; natural andsynthetic rubber and derivatives thereof; alginic acid, gelatine,casein; and mineral fibres such, for example, as spun glass, asbestos,mineral wool and the like, and fibres made of natural and syntheticresins which should be of such type that they are not rendered tackywhen the potentially adhesive resin fibres are rendered tacky byheating; also fibres and filaments made by slitting, cutting orshredding non-fibrous films, such as waste Cellophane.

The potentially adhesive resin fibre may be composed of a wide varietyof materials, and may comprise any synthetic resinous material capableof being formed into fibres which have an inherent tackiness uponheating to a temperature below that at which the non-felting fibres aredamaged or rendered tacky and which are nontacky at room temperaturesuch, for example, as

the resins formed by the polymerization of various organic compoundssuch as coumarone, inclene hydrocarbons, vinyl, styrene, sterolaldehyde, furfural ketones, urea, thiourea, phenolaldehyde resins,either alone or modified with oils, urea-aldehyde resins. amine-aldehyderesins, sulfonamide-aldehyde resins, polyhydric a1oohol polybasic acidresins, drying oil-modified alkyd resins, resins formed from acrylicacid, its homologues and their derivatives, sulfur-oiefine resins,resins formed from dicarboxylic acids and diamines (nylon type); fibresformed from synthetic or artificial rubber such for example aspolymerized butadiene, oleflne-polysulfides, e. g. Thiokol. isobutylenepolymers, chloroprene polymers and polyvinyl-halides, e. g. Koroseal,fibres formed from a resin comprising the product of co-polymerizing twoor more resins, such, for example. as co-polymers of vinyl halide andvinyl acetate, co-polymers of vinyl halide and an acrylic acidderivative, co-polymers or vinyl compound and styrol compound; and alsofibres formed from a mixture of resins, such for example as a mixture ofvinyl resins and acrylic acid resins or methacrylic acid resins, amixture of polyolefine resins and phenol-aldehyde resins, or a mixtureof two or more resins from the difi'erent classes Just named.

The resins above mentioned may be classified as:

(a) Heat-non-convertible resins such for example as glycol polybasicacid resins, vinyl resins filkld the acid type phenol-aldehyde resins,and the (b) Heat-convertible resins such for example as aglycerol-polybasic acid resin, polyolefine resins, phenol-aldehyderesins and the like.

(c) An element-convertible resin (which becomes infusible through theaction of certain elements, such as oxygen and sulfur) such for exampleas glycerol-polybasic acid-drying oils, resins and olefine sulfurresins.

For felts that are subjected to laundering or dry cleaning, thesynthetic resin fibre should be insoluble in water and inert to thedetergents used for laundering and dry-cleaning. The resins employed arepreferably those which do not soften appreciably at temperatures reachedin laundering and blocking" (as in the making of h t f l hough softeningduring blocking is not objectionable.

In the new preferred embodiment there is used synthetic resin fibrecomprising a co-polymer of vinyl acetate and vinyl chloride which fibresare made of suitable methods known in the art. This fibre resemblesrayon and is similar thereto in many respects, but it differs therefromsince it becomes tacky when heated to a temperature of from 200 F. to350 F. When heated, it becomes adhesive to other fibres in contact withit and adheres thereto upon cooling, It is tough and firm at ordinarytemperatures, insoluble in water, and inert to the agents used inlaundering and drycleaning and shows no substantial decrease in tensilestrength on being wetted.

The ratio of synthetic resin fibre to other fibre may also vary widelydepending on the properties of the two types of fibres and may beregulated to suit the purpose for which the felt is destined, but ingeneral a minor proportion, preferably from 3 per cent to 20 per cent ofthe synthetic resin fibre will be employed. Where a greater degree ofstrength or a closer bonding of the component fibres is desired, thepercentage will be relatively high, whereas in felts, such as papers ofcertain construction where it is desirable to have a comparatively smallamount of bonding of the component fibres, the percentage will berelatively small.

The synthetic resin fibre and other fibre have been mixed by a methodsuitable to the production of a particular type of felt, for example.the fibres may be mixed by carding.

The inherent tackiness of the resin fibres 5 8&-

tivated by heating the felt to an appropriate temperature, for exampleby the use of ry hot contact with heated surfaces, steam or hot water.The temperature of the heat-treatment will depend on the properties ofthe synthetic resin fibre and must necessarily be below that at whichthe felt is damaged. When the felt is cooled, the synthetic resin fibresbecome non-tacky and tough, and adhere to the other fibres, thusproviding a felt which possesses increased strength and greater tenacitybetween component fibres.

Generally, it is preferred to immerse the felt in water at orapproximating the boiling point, as it is found thatthe water carriesthe heat unlformly through the felt and accordingly reacts on thethermoplastic fibres throughout the entire felt. In certain cases,however, where it is desirable 'to obtain a surface-glazed effect onfelts, wherein the thermoplastic fibres are largely exposed on thesurface thereof, it may be more desirable to heat the fabric by surfacecontact with heated metal, such as is practiced in the conventionalheated calender, The method of heating may be carried out in whichevermanner may be selected tolcon form most'satisfactoriiy with the effectdesired in the finished felt.

The tackiness of the resin fibres may be modified by heating the resinfibres in the presence of a suitable plasticizer depending on theparticular type of resin. The plasticizer may be incorporated in orcarried by the resin fibres and/or by the non-feltable fibres and may beincorporated in the fibres at any point prior to heating. In thepreferred embodiment the plasticizer is incorporated in the resin'massprior to its formation into fibres and filaments. The plasticizer lowersthe temperature at which the resin fibres are rendered tacky uponheating. After heating, the plasticizer is preferably removed bysuitable means such as evaporation or extraction, thereby preventing theresin fibres from again being rendered tacky at the original activatingtemperature and rendering them capable of remaining non-tacky at ironingtemperatures.

The mixture of fibres may be felted in a predetermined shape by use of asuitable mold, or the felt may be shaped and given a desired form. Theshaping takes place in the case of paper felts, preferably by molding orshaping the wet paper sheet. In the case of textile felts, it ispreferable to shape the felt after its initial formation and after thethermal activation of the potentially adhesive fibres and while suchfibres are in an adhesive condition. The predetermined shape of bothpaper and textile felts may be permanently set by the deactivation ofthe adhesive or of the adhesive fibres. By this means there may beproduced a wide variety of shaped, felted structures which may be usedas substitutes for woven, knitted or netted fabrics and articles madefrom the same. As the felting and shaping process herein describedinvolves no spinning, weaving, knitting or other similar textileoperation, it is obvious that the shaped, felted structures can beproduced at a very low cost.

The invention is applicable for making various types of textile felts,such for example as "woven felts, "needle felts and pressed textilefelts.

In the case of woven felts the basis is a woven construction having afull na or pile which is felted until the woven structure is obscured.After the woven construction is shrunk and the flap felted in the usualmanner, the felt 15 subiected to heat to render the resin fibres thefelted nap fibres.

Needle felts are commonly prepared by placing a layer of unfelted fibreson one or both sides of a woven gauze and the fibres drawn partlythrough the gauze by means of barbed needles, after which the article ispressed. In this embodiment the layer of fibres comprises a mixture ofunfeltable fibres and resin fibres. After .the fibres are drawn into thegauze, the felt is subjected to heat and pressure to activate theinherent tackiness of the resin fibres to cause a permanent adhesion ofthe fibres in the layer and to effect an anchoring of the felted fibresto the gauze base.

The present invention has special application to the manufacture ofpressed textile felts such as are used for hats, chair pads, rugcushions.

sound and shock absorbers and the like. In the formation of such felts,a mixture of the unfelta-ble fibres and resin fibres is prepared as bycarding and shaped into a layer. The layer of fibres is placed betweenheavy sheets of fabric, such as canvas, preferably moistened with waterand then placed between heated metal plates which are vibrated rapidlywhen in contact with the enclosed layer, thus causing the fibres tobecome matted together in a compact layer. If desired'the layer offibres may now be heated to render the resin fibres tacky and effect apermanent adhesion of the fibres in the felted condition, or thisheating step may be carried out at a later time. The layer of feltedfibres, before or after heating, may be folded and placed in the usualfelting box provided with conventional hammers by which the layer may bepounded to a desired thickness, firmness, length, width, con figuration.etc., after which the felt is heated. if desired, to render the resinfibres tacky and the felt is then finished in the usual manner. Forsmoothsurfaced felts the layer is run through calenders which may beheated to render the resin fibres tacky.

As an illustrative embodiment of a manner in which the invention may bepracticed. the following examples are presented:

Example I A rayon staple may be cut to a length of 1.5 to 2 inches and aresinous fibre as a oil-polymer of vinyl acetate and vinyl chloride maybe cut to a corresponding length. The cut fibres may then be mixed in asuitable carding machine in the proportions of about 90% of cut staplerayon and of the resin. A textile felt may then be formed from themixture in a suitable manner, and the admixture is heated sufilcientlyto soften the resin. As a rule a temperature of about 200 F. will serveto soften the resinous fibre, and hence such temperature preferably isused. While in a heated, softened condition, the resin fibre becomesadhered to the other fibres surrounding it. causing the fibres to clingtogether. On cooling, the resinous material becomes solid and non-tackyand tough. although still adhering to the fibre surrounding it. with theresult that the fibres are substantially fixed in position. thusimparting strength and the felt.

Since certain changes in carryin out the above process. and certainmodifications in the article which embody the invention may be madewithout departing from its scope. it is intended that all mattercontained in the above description maintaining the shape of tacky whicheffects an adhesion or bonding of shall be interpreted as illustrativeand not in a' limiting sense.

The product hereinabove described is the subject matter of a divisionalapplication Serial No. 782,870, filed October 29, 1947, and. entitledTextile product.

Having described my invention, what I claim as new and desire to secureby Letters Patent is: 1. The process of making self-binding fabrichaving a woven textile base, which consists in mixing non-fusible andfusible fibres into a bat. needle punching the bat upon a textile base,and then subjecting the two plies thus formed to heat and pressure tofuse the latter fibres into an anchoring web on both sides of thetextile base. 2. The process of making self-binding fabric containing aprefabricated textile base, which consists in mixing non-adhesive fibresand potentially adhesive fibres, spreading the mixed fibres on one faceof the prefabricated base, needle-punching a substantial proportion ofsaid mixed fibres into said base, activating said potentially adhesivefibres to render said potentially adhesive fibres tacky, anddeactivating said potentially adhesive fibres to bind said non-adhesiveand said potentially adhesive fibres to said base.

3. The process of making self-binding fabric containing a prefabricatedtextile base, which consists in mixing non-adhesive fibres andthermoplastic fibres, spreading the mixed fibres on one face oftheprefabricated base, needlepunching a substantial proportion of saidmixed fibres into said base, activating said thermoplastic fibres by theapplication of heat thereto to render said fibres tacky, and coolingsaid product to bind said non-adhesive and said thermoplastic fibres tosaid base. I

4. The process of making self-binding fabric containing a prefabricatedtextile base. which consists in mixing non-adhesive fibres andthermoplastic fibres into the form of a bat, superposing said hat on oneface of the prefabricated base, needle-punching a substantial proportionof the mixed fibres constituting said bat into said base, activatingsaid potentially adhesive fibres by the application of heat thereto tovcontaining a prefabricated textile base, which consists in mixingnon-adhesive fibres and thermoplastic fibres, spreading the mixed fibreson one face of the prefabricated base. needlepunching a substantialproportion of the mixed fibres through said base to and beyond theopposite face thereof. subjecting said product to pressure andactivating said thermoplastic fibres by the application of heat theretoto render said fibres tacky while the product is under pressure, andcooling said product to bind said non-adhesive and said thermoplasticfibres to said base on said opposite faces respectively thereof.

caamrou s. FRANCIS, in.

sameness orran The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name @Dato 2,232,647 zirkmsn Feb. 18, 19412,277,049 Reed Mar. 24, 1042 2,181,048 Boeddinghius Nov. 21, um

